Red89gt

Wife's MDX reached 100k miles and I had a 50% off coupon for napa a while back and bought the NGK 6994 plugs in preparation. Couple of the plugs had resistance the whole way out and it was pretty nerve racking wondering if the steel 100k plug was taking the aluminum cylinder head threads out with it.

The middle plug on the front and back banks looked like they were NOT fully seated since factory installed since there was residue past the gasket. The other four looked fine.

All the plugs still had their stock gap and no wear damage to the electrode area's. The porcelain did have witness marks of the spark leaking out thus the brown stain at the at the base of where the porcelain meets the steel base.

Putting the new plugs in was no better, first time in my life, ended up busting out the torque wrench to install the new plugs. There was no finger tight running them in. I started them by hand to make sure straight before putting wrench on them but couldn't tell when the gasket was seated. All in all it was uneventful but it sure did create some stress and it saved me about $250 since the dealer wanted $300 pending no issues to do the job. The truck runs no different with new plugs versus old. On to the timing belt in a couple thousand more miles.

Here is a pic of the front and rear banks on the work bench as they would be in the engine, the top of the picture row would be the 3 against the firewall:



Outer plug picture:



Middle plug must have not been seated:

Red89gt

After using search tool on here seeing damage from blown plugs it is unnerving. It has me kind of stressed. I guess I might have to check them again as well. Pain in the a$$. Been working on cars for 30 years now and never had to question such an easy maintenance task. I do all the maintenance because it's so easy and I don't trust most shops, just easier to do myself. Plus I use high quality parts and save a lot of money, win win.
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blkdog444

Thank you for posting this as I just did mine (03) over the weekend and found all 6 plugs to be on the loose side. They came out showing normal use so I think they were seated and working well. The plugs were original and never change @120k miles. I'm guessing they loosen due to wear and tear at 120k and not a factory workmanship issue. I also fully subscribe to your win/win philosophy.

screaminz28

iTrader: (1)

Since you do your own maintenance, I'd suggest adding checking plug tightness to the list every 3rd oil change or so. Apparently its fairly common for them to loosen over time, especially #5.

Red89gt

Thanks, yep will be checking with oil changes for sure.

blkdog444

very good to know
will keep an eye on it esp #5
but its a pia to just check

Skirmich

I performed this change on my 07 recently.. No loose spark plugs with 72K, Replaced the stock Densos with NGK Laser Iridium. The Denso´s had wear on the electrode though.